1. Field of the Invention
The present invention relates to a rolling mill, and more particularly to an apparatus for adjusting a desired width of a horizontal roll for a rolling mill to thereby obtain a steel product having a desired shape, such as an H beam, without dismantling the roll from the roll stand thereof.
2. Description of the Related Art
Known in a prior art is a universal rolling mill which includes a horizontal roll having a width which can be varied to obtain a desired dimension of an H beam. Various methods of adjusting a width of the roll, with or without dismantling the roll from the roll stand, have been proposed. Japanese Examined Patent Publication (Kokoku) No. 1-33243, for example, discloses hollow rolls having, at the ends thereof, screw threads to which respective thrust rings are screwed, and a roll shaft is axially and slidably inserted through the thrust rings and hollow rolls. The hollows rolls have flange shaped rolling portions axially spaced from each other; the rolling portions thereof coming into contact with a material to be rolled. Clutch members, which are usually disconnected, are provided for a selective connection of adjusting gears with respective thrust rings, when an adjustment of the effective width of the roll is desired. The rotation of the adjusting gears by suitable actuators causes a mutual rotating movement to be generated between the thrust rings and the hollow rolls, which causes a distance between the rolling portions (the effective width of the roller) to be varied. This prior art suffers, however, from a drawback in that no provision is made for a prevention of a mutual rotation between the rolls and the thrust rings when a usual material rolling operation is carried out, and therefore, the effective width of the rolls may be accidentally varied. An arrangement of thrust rings at the axial ends of elongated hollow rolls causes a rolling reaction force to be transmitted to the thrust rings via the lengthy hollow rolls, which force is generated in end surfaces of the rolling portions when the material is subjected to a rolling process, resulting in an increased variation of a distance between the remote ends of the rolling portions and causing the precision of the dimension of an inner web of the rolled product to be worsened. Furthermore, there is also a drawback in that a process for obtaining a centering of the roll with respect to a pass line is complicated.
As technique which can overcome the above-mentioned drawback, the assignee of the inventor of the present invention has proposed an apparatus for adjusting a width of a roll without dismantling the roll from the roll stand (housing), in Japanese Unexamined Patent Publication (Kokai) No. 62-176604. The apparatus in this prior art is provided with a shaft having an outer screw thread portion formed thereon, and an axially spaced apart horizontal fixed roll and horizontal movable roll, which are axially slidably inserted to each other, are arranged over the screw thread portion. The horizontal movable roll is provided with a roll width adjustment screw which is in screw engagement with the outer screw thread portion, and a rotating means such as a gear is provided for rotating the roll width adjustment screw to thereby adjust the axial movement of the movable roll with respect to the fixed roll, whereby a desired effective width of the roll is obtained. This improved apparatus suffers from a drawback in that the adjustment of the roll width in the direction of reducing the width is difficult, since a sleeve member for controlling the width of the roll is located between the rolls and may come into contact with the rolls when they are adjusted to reduce the distance therebetween. Furthermore, this prior art suffers from a drawback in that a large drive force is required to obtain a quick adjustment of the roller width, which inevitably increases the dimension of the apparatus and prevents it from being housed in the rolling mill housing as is. To avoid this difficulty, it has been proposed to provide a drive source in the stand housing, but this makes the replacement of the rolls complicated and time-consuming.